Accumulator bladder



March 26, 1946. N. DE KISS 2,397,248

$ AGCUMULATOR BLADDER Filed Aug. 25, 1943 3a 4? l6 24 /a 20 l4 V "if m:26

1 L 27 4 T I I I I L ELL; 5

- INVENTOR. NICHOLAS DE KISS A TTOHNEY Patented Mar. 2 6, 1946 Nicholasdc Kiss, North Hollywood, Calif assignor, by mesne assignments, toBendix Aviation Corporation, South Bend, Ind., a corporation of DelawareApplication August 25, 1943, Serial No. 499,967

.6 Claims. (Cl. 138-30) This invention relates to hydraulic-pneumaticaccumulators of the bladder type for use in hydraulic systems, forexample in the hydraulic systems of airplanes, and is a continuation inpart of de Kiss, Serial Number 470,359, filed December 28, 1942.

Accumulators are used for storing hydraulic fluid under pressure. Ingeneral, they comprise a shell having an air. connection and a hydraulicconnection, with a flexible partition between the air and hydraulicfluid so that the hydraulic fluid may act against the air withoutpossibility of contamination by the air. The hydraulic fluid actsagainst the compressed air so that pressure will be maintained in thestored hydraulic fluid. It has been found that accumulators of thebladder type can be made lighter than accumulators of the diaphragmtype, and it i with bladder type accumulators that this invention isconcerned.

One of the tests to which all accumulators must be subjected is theapplication of a hydraulic test pressure which is usually double ortriple the systempressure, when all air is removed from the accumulator.In such tests the bladder completely collapes, folding back upon itselfand being pressed against the air inlet. To prevent the bladder frombeing extruded into the air inlet, and-thereby damaged, metal discs areinserted in the bladder to bridge or cover the air inlet hole.Therefore, means must be provided to center the metal discs uponcollapse of the bladder so that they will fit over thealr inlet. Anothervery important reason for centering the lower half of the bladder.within the upper half relates to the problem of stretch. At lowtemperatures most or the synthetic rubbers suitable for use in hydraulicsystems are quite brittle and stretch should be avoided. For this reasonthe lower half must fit evenly into the upper half and not be cocked atan angle where one wall might grab the other and form a'chord whichwould be stretched.

A further reason for promoting even collapse of the bladder relates tothe trapping of fluid. For greatest volumetric efficiency the upper halfof a bladder must stick closely to the accumulator shell so that no oilpockets will be formed. Therefore. the upper half of the bladder must beheld closely to the shell, particularly at the midsection where th fold"takes place upon the collapse of the bladder. I

Also. means should be provided to cause a radius oi bend in the bladderat the point where tremely brittle at very low test temperatures and maycrack ii a sharp bend is imposed upon it.

The present invention satisfies these require ments, and in generalcomprises a bladder which has a reinforcement along the lin of folding.The reinforcement causes the stationary part of the bladder to maintainits shape, preventing the trapping of oil, and centering the discs. Itis often desirable to make the stationary portion of the bladder thickerthan the flexible part, to aid in maintaining the shap of th stationaryportion. In such cases the thick wall may terminate abruptly at thesection of folding, and when the thinner flexible part folds, there isan appreciable radius oi bend which prevents cracking of the bladdermaterial at low temperatures. In such a bladder the reinforcement ispreferably imbedded in the stationary part of the bladder near theabrupt termination of the thick portion. In other constructions, aninternal head is provided to give an appreciable radius of bond. inwhich case the reinforcement may be placed in the bead.

It is therefore an object of the invention to provide an accumulatorbladder having its stationary portions reinforced to aid in maintainingits shape.

It is an. object of the invention to provide an accumulator with abladder which will center metal discs over the air inlet of theaccumulator.

Another object is to provide a bladder with an internal head which hasstiffening means to hold the beaded portion of the bladder against theaccumulator shell.

Still another object is to provid an accumulator-bladder which willsimultaneously provide a radius of bend for the bladder material andalso center metal discs with respect to an air inlet.

In the drawing forming a part of this specification:

Figure 1 is an elevation view, in full section, of

an accumulator oi the type embodying the present invention; and

Figure 2 isa fragmentary view of an accumulator shell and bladdershowing a modification of the invention: and

Figure 3 is a sectional view of a mold for the bladder of Figure 2,showing one step in the forming-process.

Referring to Figur l, a shell in has welded to the bottom thereof athreaded hydraulic outlet fitting i2 through which hydraulic fluidenters and leaves the accumulator. Welded to the upper threaded at 18and provided with a shoulder l8 and an inwardly projecting lip 20.Fitted within shell Us a bladder 22 having a preformed shapesubstantially like the interior of shell I. Formed on the upper end ofbladder 22 is an outwardly projecting lip 24 which hooks over theinwardly projecting lip 20-of collar I4. The bladder 22 is preferablyformed of an upper molded part 26 and a lower molded part 23 vulcanizedtogether along the tapered surface 25. It will be noted that the upperhalf 26 of the bladder 22 is thicker than' the lower half 23. The lowerhalf 23 may be tapered in section from the bottom of the thicker half tothe bottom where it may be thinner. The thick upper half 26 terminatesabruptly in a curved end 29. .Molded within curved end 29 is acontinuous solid spring 21 which stilfens the end 29 and, beingcircular, acts as a compression member to hold the upper portion of thebladder against the shell l0. Secured to the bottom of bladder 22 is alower disc 28 and an upper disc 30 held together by a screw 32. Lowerdisc 28 fits over hydraulic outlet l2 when the bladder is fully extendedas shown in full lines, and upper disc 30 fits over the. air inlet asshown in dotted lines.

Placed wlthin collar :4 is a plug member 34 which rests on shoulder l8and which fits snugly against the upper end of bladder 22 and holdsbladder lip 24 in contact with collar lip 29. An annular nut 36 isthreaded into collar l4 to hold plug 34 in place. A cotter pin 38 passesthrough collar I4 and fits in a slot 49 in nut 36 to lock nut 36 inposition. Plug 34 has a central hole 42 2,se7,24e- H fluid under fullpressure is then pumped in therethrough into which is threaded an airvalve element 44.

In inserting the bladder 22 into the accumulator shell for assembly,opposite sides of the bladder and spring are pressed together and thebladder rolled about this elongated shape. The elongated mass is thrustinto the opening of collar l4 and then allowed to uncoil, at the sametime being manually straightened. The spring 21 is highly desirablebecause of practically no yielding under compression. This insures thatthe bladder 22 will at all times fit closely the shell l9, preventingthe trapping' of liquid. The spring 21 may also be inserted in thebladder after it is molded by molding an annular cavity therein andfitting the spring into the inside of the end 29.

In operation, air is inserted into the accumulator through valve element44 and the bladder assumes the general shape as shown in full lines.There it will be noted that lower disc 28 bridges the opening ofhydraulic outlet !2, so that the air pressure will not force the bladderinto the outlet I2 and damage the bladder by extrusion. Outlet I2 isthen connected to a hydraulic system including a pump, and hydraulicfluid under pressure enters the accumulator forcing the bladder 22upwardly until the air is compressed to a pressure equal to thehydraulic pressure. The thinner. more flexible part of the lower halfyields first, collapsing regularly into the upper half so that a rollingmotion is promoted which prevents trapping of fluid in the lower-half.There'- after, hydraulic fiuid'will be added to or subtracted from theaccumulator according to the demands of the hydraulic system and-thepres-- sure available from the pump of the hydraulic system. At alltimes spring 21 aids in holding the upper bladder portion 26 againstshell I0, preventing the trapping of liquid in that region.

When it is desired to test the accumulator, the air valve 44 is openedallowing all air to escape from the inside of the bladder 22. Hydraulicthrough fitting l2 andthe bladder gradually collapses, the thin lowerhalf of the bladder projecting upwardly into the thicker upper half ofthe bladder, which maintains its position against the shell Ill becauseof its thicker section. The end 29 guides the lower half evenly into theupper half of the bladder because it is a thickened and reinforcedportion, which will resist deformation to a relatively greater extentthan the thinner wall of the lower half. The final state is that shownin broken lines in Figure 1, wherein the lower half of the bladder ispressed tightly against the upper half, and the disc 30 is centered overhole 42. It will be noted from an examination of these broken lines thatthere is an appreciable radius to the bend about end 29.. This radius isvery important in preserving the blad der because at a low temperaturesuch as 65 R, which may be encountered in actual use, the bladdermaterial becomes somewhat brittle and often cracks if folded fiat uponitself without a radius being provided for the bend.

The bladder of Figure 2 differs from that of Figure 1 in that a beadreplaces the curved end 29, and the spring, which is inserted in thebead, is of the coiled type instead of solid metal. A bladder 4| fitsthe shell l0 closely and has a thick upper portion 43 and a thin lowerportion 45 with an inwardly projecting bead 46 formed at the juncture ofthe two portions. Imbedded in bead 46 is a continuous coiled spring 48.The bead 46 gives an appreciable radius of bend to the bladder when thelower half is folded inside the upper half as shown in broken lines.

. The mold for making the bladder 49 of Figure 2 is shown in Figure 3.The mold is composed of an outer member 50 and an inner member 52 havingan annular recess 54 for forming the bead. A piece of uncured bladdermaterial 46A is placed on the inside of recess 54 and the continuousspring .48 is placed over it. Thereafter the bladder material is pouredinto the mold and cured, part 46A being formed integrally there-. with.The mold part 52 is preferably made in several parts which may beremoved through the. mouth of the cured bladder. This preventsstretching the opening of the bladder around the inner mold to removeit. The bladder may be of any relatively flexible material, such asplastic or other rubber-like substances. The coiled spring constructionpermits the manufacture of a one-piece bladder.

The invention has been described in detail with references to particularembodiments thereof. It is not limited to these embodiments, norotherwise limited, except by the terms of the following claims.

I claim:

1. A bladder type accumulator comprising a shell having a liquidopening, abladder secured in said shell, means to apply a compressiblefluid on one side of said bladder, the other side being exposed to theliquid admitted through the liquid opening, one part of said bladderbeing thick and adapted to remain substantially stationary in saidshell, the other part of said bladder being thinand relatively flexibleso that it will telescope into said thick portion, said thick portionforming a curved end at the juncture with the thin portion so that a padof material is formed about which thethin portion may fold with anappreciable radius of bend to prevent cracking at low temperatures, anda reinforcement in said curved endand having a generally roundtransverse. cross section, and a reinforcement at the end opposite theend afllxed, said bladder also having an internal annular bead tocentralize said reinforcement on said opening about which the bladder isfitted and to provide a radius of bend when said bladder is folded uponitself, and spring means reinforcing said annular bead to preventcollapse of the same. i

3. A bladder type accumulator comprising a shell having a hydraulicopening, a flexible bladder secured in said shell, means to apply a gasto one side of said bladder, the other side being adapted to contactliquid admitted by the hydraulic opening, said bladder having astationary portion and a flexible portion which is adapted to telescopeinto said stationary portion, an 'internal bead on said bladdersubstantially at the line of juncture of the two portions, so that anappreciable radius of bend will be present when the portions aretelescoped, and reinforcing means at said bead to cause the bladder tomaintain its shape so that folding will occur at the juncture of theportions.

4. An accumulator having, in combination, a rigid container havingopenings at opposite ends, a bladder of molded flexible materialdisposed within said container and having one end secured to thecontainer and communicating with one of said openings, an inturnedannular rib of rounded cross-section molded around said bladderintermediate the ends thereof, and a flexible wire reinforcing member,embedded in said rib.

5. An accumulator comprising a shell having an air opening and ahydraulic opening, a flexible bladder secured therein and separatingsaid air opening from said hydraulic opening, said bladder having athickened portion normally conforming to the shell and a thinner portionadapted to telescope into said thickened portion, said thickened 4portion terminating abruptly forming a termination line which allows thethinner portion to fold with an'appreciable radius of bend when theportions are teiescoped, and spring means of material substantiallystifler than the bladder material reinforcing said thickened portionadjacent said termination line to resist collapse of same. I

6. A bladder type accumulator comprising a shell having a liquidopening, a bladder secured in said shell having a stationary portionwhich flts the shell closely and having a flexible portion adapted totelescope into the said stationary portion, and spring means of materialsubstantially stifl'er than the bladder material reinforcing saidbladder at the line of juncture of the portions, so that the randomcollapse of the stationary por,

tion is avoided.

NICHOLAS m: KISS.

